6g72 Rebuilt Ecu, New iac. NEED HELP

I had my Ecu in my 90 3.0 rebuilt as a capacitor had leaked and my truck wouldnt start it all. Well the guy that rebuilt it said I needed to change the Oem Iac that I had as they were known to cause the Ecu to burn up. For whatever reason the new Iac makes my truck fluctuate between 1k and 2k rpms while its cold. Then when warm it idles about 3-400 more rpm then normal. When I put the old iac back in the truck runs perfect. No high Rpm or fluctuating. Anybody else run into this problem or something similar when changing their iac? Any help i would appreciate!
Ps I bought another iac just to make sure the new one i got wasnt a dud from factory. Still having same problem.

Make sure you ordered the right part number. It is true, the old IAC will eventually fail and short out. There are no protective measures between the IAC and the circuit that controls it on the ECU board. They can destroy an ECU in short time and without warning.

3000GT guys have the same problem and only run the black plastic OEM units. Oddly they are the exact same part numbers between the two. I suggest you use the same.